Matrix/array completion

It seems to me that once the top row and the left column have been filled-in with incrementally changing entries, Excel is ideally suited to complete the rest of the array. I do not know what function will do this. Can someone tell me please ?

Excel may be the solution, but the answer depends on what goes in the table. We are only left to guess ...

I want to use EXCEL to summarise annual expenses. I have 'manually' set it up before, but it is tedious & laborious, but should be a cinch for EXCEL.

I set up a workbook with 13 sheets - one for each month - plus a sheet for totals. In the Totals sheet I have 12 columns - one for each month - and rows for categories of expenditure. The cells should contain the linkages from the totals in each category in each month. Once I have all the left-most column filled in with links to January totals, and have created a top row with the links to the first expenditure category for each month, I then want the rest of the table to be completed automatically, rather than manually.
Surely there is a function that will do this !

I had not ticked for email notification, so did not know there had been a response - hence the delay.